This invention relates to apparatus for actuating a plurality of probes into electrical contact with a plurality of generally planar test points on a test member.
Circuit board verifiers are generally known employing an actuator assembly for moving a plurality of electrical test probes into electrical contact with a plurality of generally planar test points on a circuit board under test.
The probes are generally elongated, having a probe head at one end for making electrical contact with a test point on the circuit board and an opposite end electrically connected to a test device such as a circuit board analyzer. Continuity and lack of continuity are detected by the analyzer between the various test points on the circuit board for use in determining if the circuit board is proper or defective.
Different approaches have been utilized for bringing the array of test probes and the circuit board under test into engagement. One class of these devices is vacuum actuated and employs an array of probes mounted in a fixed backing member. A stiff backing, for receipt of a circuit board for test, is flexibly mounted so that it is movable relative to the fixed backing member. Holes are cut through the stiff backing corresponding to the location of test points on the circuit board through which the probes may extend. A sealing member is mounted in opposing relation to the backing member. The chamber is evacuated, drawing the sealing member and the circuit board, and the stiff backing, in the direction of the probes until the probe heads are in electrical contact with the circuit board.
Problems exist with such an arrangement. By way of example, the pressure required to draw the circuit board towards the probes causes the backing in which the probes are mounted and the printed circuit board to bow. Telescoping spring probes are used to compensate for the variations in the circuit board and/or the backing (and hence the position of the ends of the probes). However, the telescoping spring probes are quite costly since they must be made in miniature size in order to allow very close spacing, for example, in the order of 0.100 inch on center.
Other arrangements have been made for bringing an array of probes and circuit board together for test. For example, a movable platen has been used for engaging a circuit board with an array of spaced contact probes. However, such arrangements are generally slow and costly.